reading this:
https://www.thirdgen.org/techbb2/sho...hreadid=214156
I think I rad this Tim tutorial 100 times in 2 years, but only now i read this:
"The VE table values are not used and are not needed for calculating a target AFR."

This means that when PE is active I have not to care of the VE value and the only way to change the real AFR at wot is achieved using the PE %Change to AFR vs. RPM table ?

So if I have a value of 10 or 44 or 99 on the VE table on the 4000 rpm range and 95 Kpa (for sure I'm in PE mode...) there is no difference??
The ONLY important thing is the value that I have in the PE table PE %Change to AFR vs. RPM table in relationship with the Coolant table at L860D ?
I'm confused.
Let's assume I have a WB and I see that at WOT at 4000 rpm and 95 kpa I'm at 12,5 AFR.
Let's assume i need less fuel. Say 12.8.
If I have a value of 85 in the VE table and I lower this value to say 80 The WB will read always 12.5:1 AFR?
Thaks for your help.
-Beppe-

 

A misunderstanding of the terminology. The target AFR is the AFR the ECM is using to calculate the injector PW. The lower the target AFR the larger the PW. The higher the target AFR the smaller the PW.

The target AFR is the desired AFR for the current conditions. When in closed loop it is typically 14.7:1. In WOT/PE mode it is richer, along the lines of 12.2:1 to 12.8:1. In open loop it can vary from 10:1 through 15.8:1 (ballpark numbers). The calculation and selection of the target AFR has nothing to do with the VE values.

Changing the VE values will change the PW which in turn changes the observed AFR. It does not change the target AFR.

The purpose of tuning the VE tables is to make the observed AFR match the target AFR.

RBob.

 

Target AFR and real AFR are not the same thing!

The target AFR has nothing to do with the VE table, as Tim pointed out. If you set up the ECM on a bench, and burnt two different chips with totally different VE tables - for example, one chip's VE tables has values that are exactly half of the other chips' tables - then for a given RPM/MAP condition, the target AFR would be the same. The target AFR is not dependant upon the VE tables.

But now you run these two chips on the ECM bench. Sure enough, the ALDL data stream reports the same target AFR for both. But then you notice the pulsewidths are different...very different. The real AFR (if you run both of these chips on the same real motor) would be very different!

No. You absolutely have to care about the VE value. The PE%change table just helps you arrive at what AFR you want to run, the VE tables tells you how much air there is.

That is correct.

Basically, what you want to do (or at least, the way I prefer to tune) is this: first, set your TARGET afr. Let's say we want it to 12.5:1, so we set it to have 17.5% percent change to AFR. so, our target afr is 12.5:1.

Then you make a wide band run, and discover that at say, 4000 your actual afr is 12.5, 4400rpm your actual afr is 12.8 and at 4800 it's 13.2.

So, you leave the VE cell for 4000 alone (it's perfect), you raise the spot for 4400 a little bit, and the spot for 4800 a bit more than a little bit.

once you have your VE table tuned to match the target AFR, then you can simply change the %change table to change your desired AFR, and since the VE tables are accurate, you won't need to touch them again.

edit: looks like rbob beat me to it and was more concise to boot! i'll leave this up anyways in case it helps.

 

Most people doesn't think that way, especially in terms of WOT recalibration. To the average "tuner", getting the desired a/f readings is all that matters. I was using AFRtuner to get the desired A/F ratio for my formula. The downside was that my ve tables turned out to be WAY off. Brought me back to tuning wot through the VE tables. Guess that might also work for a modded MAF , change the upper tables to match target A/F ratio (then move on to PE tables). Guess one would have to know the target a/f ratio in order to match it.

 

Reading all your reply I'm fine now...
It is like I was thinking.
Only the TARGET AFR has nothing to do with the VE values.
....and I know tat the TARGET AFR is way far to be the correct AFR.
...The real AFR (detected with a WB) has the VE vales as a term of it.
Now i nedd only a WB
The zeitronix is a good way?
With this unit I can continue to read AFR, rpm and also MAP values???
or only AFR and rpm?
Thanks
-Beppe-

 

 

That's means I have to serch in the archive??
Done.
I've not yet the answer...
So I post again: With this unit (Zeitronix) I can continue to read AFR, rpm and also MAP values???
My interest is in the Map (Kpa) reading.
Thanks
-Beppe-

 

I didn't mean it in the manner in which you took it. However, I can see why you took it that way. I was happy you found an answer to the first question you posed

I don't know about the Zeitronix unit. However, most wideband sensors will make you purchase additional equipment for logging extra inputs. If I were you I would just use the Wideband hack for the AUJP and log the AFR of the wideband in the datastream. However, you will want to obtain a voltage-to-AFR graph of whatever wideband you use and update the wideband hack to be consistent with whatever wideband you used. The hack is designed to be used with the DIY-WB meter. That's what I used and it worked perfectly. I even wrote a program that will insert and remove this hack easily. Search on 'AFRTuner'.

Tim

 

A friend in Germany uses the Zeitronix WB . I believe the box has 3 or 4 analog input
channels - Tach signal (taken directly from the coil), plus pins for TPS, MAP, and maybe(?)
something else. (I haven't seen the unit, just the logs.)

Zeitronix includes some graphing software to display the data - you can download a copy
from them.

Look at their web site to be sure about the inputs. My friend gets good results from his,
but I don't know the data sample rate when all channels are running. I think(?) the bandwidth
limit is the serial connection on the PC, and it is probably similar to or slower than the Dataq
unit I use (120 data points/ sec on each of 2 channels).

At the Dataq website there is a new USB ADC that overcomes the limit of the serial UART(?).
I didn't read all the details (my old laptop has no USB port), but if you want very high speed
data you might take a look at it.
http://www.dataq.com/products/startkit/di158.htm